Your mission is to survive long enough to wake up. For every room you visit, another 6 minutes goes by, and at 8:12 the alarm clock will ring, and save your life.
Your secondary objective is to increase your dream-state. You start with a "bad dream", but by killing monsters, and collecting chalices, you can get much worse dreams, like "horrible dream" or "deadly vision". Your dream-state is displayed in text-form at the top of the screen, and does not affect the game in any other way.
This is a horror game, and you will face zombies, bats, ghosts, and other terrifying creatures. If they touch you, you lose one of your five lives. You can collect different items, like guns, crucifixes, clocks, and other stuff. Your inventory can hold up to three items at once.
You can kill some enemies with the gun, but many are immune to it. Crucifixes can freeze enemies, and clocks slows them down.
The game consists of a huge maze of interconnected rooms. It's easy to get lost, and the game is almost impossible to complete, even if you cheat. So this is for anyone who wants a big challenge.